Question: What are the platforms in Half-Life that are set in the foundation date of 1991-9-17?
Paraphrase: What are the Half - Life platforms set in the 1991.9 - 17 foundation date?
SPARQL (Wikidata): SELECT ?answer WHERE { wd:Q752241 wdt:P400 ?answer . ?answer wdt:P571 ?x FILTER(contains(YEAR(?x),'1991'))}
Answer: Linux